One vertex per element, one color per generator, with an edge from x to x·s.
(1,2)(3,4)(5,6,9,12)(7,11,8,10)(13,14,20,23,19,24,17,26)(15,22,25,18,16,21,27,28)(5,6)(7,10)(8,11)(9,12)(13,15)(14,21)(16,19)(17,27)(18,26)(20,25)(22,24)(23,28) involution — undirected(2,4)(5,7,9,8)(6,10,12,11)(13,16,19,15)(14,22,24,21)(17,25,20,27)(18,26,28,23)(5,7,9,8)(6,11,12,10)(13,17,19,20)(14,23,24,26)(15,25,16,27)(18,22,28,21)(5,8,9,7)(6,11,12,10)(13,18,20,21,19,28,17,22)(14,16,23,27,24,15,26,25)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.